ArtistGNDPhotography/Getty ImagesWe’ve all been there. You spend an hour in the gym, and before you even reach the change room, you start thinking about our favourite takeaway meal – after all, you’ve earned it! Before long, you’re tucking into a super-sized meal. Then the guilt hits: what was the point of exercising to burn all those calories if it just makes us eat even more calories? But while this might be a familiar pattern, it’s not necessarily a super-sized hunger at play. Let’s see what the science says. How exercise impacts our appetiteWhile many people report that exercise makes them hungry, the science is more nuanced.In the short term, a bout of exercise can actually suppress appetite. A meta-analysis of 20 studies found exercise reduced the hunger hormone ghrelin while increasing hormones associated with fullness, including PYY, GLP-1 and pancreatic polypeptide.But this effect is temporary. A more recent systematic review and meta-analysis found exercise suppressed appetite initially, but this effect wore off 30–90 minutes later.So exercise isn’t an appetite-suppression strategy. Rather, there appears to be a short window after exercise when our appetite may be dampened before it returns to normal.There is an important distinction between what happens after one workout and what happens when we exercise regularly.A systematic review of exercise training in adults who were above a healthy weight or who had obesity found a small increase in hunger levels while fasting. However, there were no clear or consistent increases in post-meal or daily hunger, and exercise did not substantially increase average energy intake.In other words, if you’re exercising more, you may well feel hungrier at some point. That’s not your body “fighting” exercise – it’s a normal physiological response to having expended more energy. People don’t necessarily compensate by eating back all the energy they have used.Does exercise intensity matter?A systematic review and meta-analysis of 13 randomised controlled studies found both short bursts of high-intensity exercise (interspersed with recovery) and moderate-intensity continuous exercise temporarily suppressed appetite. High-intenstity exercise suppressed participants’ appetites a little more, though differences weren’t consistent.But this doesn’t mean you need to start doing high-intensity interval training to control your appetite. The bigger lesson is our appetite can change temporarily in response to exercise, and people respond differently. Choose forms of physical activity you enjoy and can realistically keep doing. Enjoyment is an important part of maintaining regular exercise, and regular activity is far more valuable than choosing a particular workout simply because it produces a short-term hormonal effect.How much exercise will result in weight loss?The amount of exercise you need depends on your goal. For general health, adults should aim for at least 30 minutes of moderate-to-vigorous activity on most days, plus regular light activity and muscle-strengthening exercises twice a week. For weight loss, more is needed. Research suggests around 60 minutes of moderate-intensity activity a day may be required to achieve meaningful weight loss from exercise alone. So why can you sometimes feel ravenous after exercising?The answer isn’t necessarily that exercise has “switched on” your appetite. Several things can be happening at once.First, there’s the simple biology: if you’ve expended a substantial amount of energy, your body may eventually respond by increasing hunger as it works to restore energy balance. The more energy you expend, the more likely it is that genuine hunger will appear later.There are also psychological and behavioural factors.After exercising, we may give ourselves permission to eat more because we feel we’ve “earned” it. Research suggests people can be more likely to seek a food reward when they perceive an activity as exercise rather than simply as something enjoyable or recreational.Hydration can also matter. If you’ve exercised while dehydrated, thirst and hunger can sometimes be difficult to distinguish. But this shouldn’t be interpreted as meaning that post-exercise hunger is simply thirst in disguise. If you’ve expended a lot of energy, genuine hunger is a perfectly normal response.So don’t fear hunger after exercise – but don’t automatically assume you’ve “earned” a super-sized meal either.How to manage your post-exercise hungerResearch suggests regular exercise can reduce our desire for high-energy foods and and help reduce overeating.But if your post-exercise hunger is genuinely derailing your weight goals, here are some strategies that might help:1. Hydrate firstAfter exercise, have some water and give yourself a moment to check in with your body. If you’ve been sweating heavily or exercising in hot conditions, replacing fluids is important.2. Check whether you’re genuinely hungry or just want a reward Real hunger comes on gradually and has distinct physical cues: a rumbling stomach, low energy, a headache, light-headedness and difficulty concentrating.3. Eat if you’re genuinely hungry Never deprive yourself of food. Your post-exercise hunger is your body working more efficiently and responding to increased energy and metabolic demands. 4. Reach for nature first Have a filling post-exercise snack ready to go. Choose foods that are filling and nutrient-rich, such as:a handful of nutsGreek or natural yoghurt with berriesa piece of fruit with a handful of nutswholegrain toast with avocado or cottage cheeseboiled eggs with wholegrain toasthummus with vegetable sticksa glass of milk.These foods provide a combination of protein, fibre and healthy fats, which can help keep you satisfied until your next meal. Read more: The last 5 kilos really are the hardest to lose. Here’s why, and what you can do about it The Charles Perkins Centre studies the science of obesity and weight loss. You can learn more about our clinical trials here.Nick Fuller works for the University of Sydney and RPA Hospital and has received external funding for projects relating to the treatment of overweight and obesity. He is the author and founder of the Interval Weight Loss program, and the author of Healthy Parents, Healthy Kids with Penguin Books.